求未知数．ⅹ：=：4； 6.5：x=3.25：4； （x+7）：6=7：2.1．
直接写出得数．+= ﹣= ×2= ×= ÷3×÷3== 12×= ×14= ÷4= +÷+=
直接写得数+= 3+1.75= ÷= ×=×= ﹣= += ×0+3=（+）×= ×÷×=
口算下面各题．﹣= += ﹣= 2÷= ×6= ÷=×6= ×= ﹣= ÷= ÷= ×=×= ÷= ÷= 6.4÷0.08= 4﹣2.92= ÷=
直接写得数：1﹣= ×= ÷2÷= 2×80%=+= 15÷= 35×= ×÷×=
直接写出得数．﹣= ×= 12×= 1÷== = 1.6×4×0.25= 0÷=
=
：4； 
+
= 
﹣
= 
×2= 
×
= 
÷3×
= 12×
= 
×14= 
÷4= 
+
+
+
= 3
+1.75= 
÷
= 
×
=
×
= 
﹣
= 
+
= 
×0+3=
+
）×
= 
×
÷
×
﹣
= 
+
= 
﹣
= 2÷
= 
×6= 
÷
=
×6= 
×
= 
﹣
÷
= 
÷
= 
×
=
×
= 
÷
= 
÷
= 6.4÷0.08= 4﹣2.92= 
÷
=
= 
×
= 
÷2÷
+
= 15÷
= 35×
= 
×
÷
=
﹣
= 
×
= 12×
= 1÷
=
= 
= 1.6×4×0.25= 0÷
=
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